1. Field of the Invention
The present invention relates to a transparent autostereoscopic image display apparatus, enabling, e.g., an improved telepresence, and to corresponding methods.
2. Description of Related Art
A variety of technologies related to telepresence and telecollaboration are known. A recent comparative evaluation of different display technologies for collaborative design review can be found in the report [Hou09] (Ming Hou, Justin G. Hollands, Andrea. Scipione, Lochlan Magee, Mike Greenley: “Comparative Evaluation of Display Technologies for Collaborative Design Review”, Presence, Vol. 18, No. 2, 125-138, April 2009).
The simplest form of videoconferencing can be achieved with a standard PC with a 2D monitor, a video camera, and equipment for audio recording and playback. Prominent examples for these types of systems are Microsoft Livemeeting (http://office.microsoft.com/livemeeting, accessed: Aug. 27, 2009), Skype (http://www.skype.com, accessed: Aug. 27, 2009), or similar software suites. While such systems work reasonably well for basic communication between two persons, they are less suitable to support collaboration between larger groups. Moreover, they provide only a partial, 2D video of the remote person. Natural full body interaction including 3D appearance, gestures, or eye contact is impossible to achieve.
More realistic 3D visualization can be achieved by using stereo displays. Simple stereo displays for single persons ([Hou09]) require additional equipment such as LCD-based or polarized glasses and additional head tracking and hence are obtrusive for the viewer.
Autostereoscopic displays can produce a 3D image without requiring such additional equipment. Such displays are known, e.g., from [Perlin00] (Ken Perlin, Salvatore Paxia, Joel S. Kollin: “An autostereoscopic display”, SIGGRAPH 2000, pp. 319-326, 2000), from DTI (http://dti3d.com, accessed: Aug. 27, 2009), or from [Kitamura01] (Yoshifumi Kitamura, Takashige Konishi, Sumihiko Yamamoto, Fumio Kishino: “Interactive stereoscopic display for three or more users”, SIGGRAPH 2001, pp. 231-240, 2001). However, due to fixed lenticular lenses or parallax barriers, they are restricted to a very small, discrete set of different viewing positions and a small working area. Moreover, both types of displays are generally only available as desktop monitors. Displaying collaborating persons in their actual size and in 3D is impossible with current standard display technology.
Collaborative work can be improved by using virtual workbenches known from [Agrawala97] (Maneesh Agrawala, Andrew C. Beers, Ian McDowall, Bernd Fröhlich, Mark T. Bolas, Pat Hanrahan: “The two-user Responsive Workbench: support for collaboration through individual views of a shared space”, SIGGRAPH 1997, pp. 327-332, 1997), augmented reality techniques known from [Billinghurst02] (Mark Billinghurst, Hirokazu Kato: “Collaborative augmented reality”, Commun. ACM 45(7), pp. 64-70, 2002), or robotics, see [Machino06] (Tamotsu Machino, Satoshi Iwaki, Hiroaki Kawata, Yoshimasa Yanagihara, Yoshito Nanjo, Kenichiro Shimokura: “Remote-collaboration System using Mobile Robot with Camera and Projector”, IEEE International Conference on Robotics and Automation, pp. 4063-4068, 2006), which embed the actions or instructions of the virtual collaborator visually into the real world.
Due to this integration into the actual working environment, collaborative tasks can be performed in a more natural, unobtrusive way. But in many augmented reality application scenarios, persons still have to wear specialized display and tracking devices such as a head mounted display. Moreover, these types of systems focus on embedding purely virtual objects into the real view of a person. An integration of a fully realistic 3D rendering of the collaborating person is currently infeasible with such systems.
Proposals for larger scale systems to embed collaborating persons virtually into real office or working environments are generally based on complex multi-camera and multi-projector systems such as the one known from [Raskar98] (Ramesh Raskar, Greg Welch, Matt Cutts, Adam Lake, Lev Stesin, Henry Fuchs: “The Office of the Future: A Unified Approach to Image-based Modeling and Spatially Immersive Displays”, SIGGRAPH 1998, pp. 179-188, 1998) or [Kauff02] (Peter Kauff, Oliver Schreer: “An immersive 3D video-conferencing system using shared virtual team user environments”, CVE 2002, pp. 105-112, 2002).
The most advanced, large-scale telecollaboration system up to date has been the blue-c project described in [Gross03] (Markus H. Gross, Stephan Würmlin, Martin Näf, Edouard Lamboray, Christian P. Spagno, Andreas M. Kunz, Esther Koller-Meier, Tomás Svoboda, Luc J. Van Gool, Since Lang, Kai Strehlke, Andrew Vande Moere, Oliver G. Staadt: “Blue-c: a spatially immersive display and 3D video portal for telepresence”, ACM Trans. Graph. 22(3), pp. 819-827, 2003). Here the collaborating person is located in a small room, a so-called cave. The environment and collaborators are projected in full 3D onto the walls of the room. Cameras record each person from multiple viewpoints such that it can be reproduced as a 3D model at a remote Blue-C installation. The Blue-C system provides a realistic immersive experience to the user, with a three-dimensional reproduction of collaborators, their gestures, mimicry, and other important stimuli. However, each cave can contain a single person only, the complete environment has to reproduced virtually, and it is impossible to integrate such a system into standard office spaces or more complex working environments due to the complex hardware and installation requirements.
Many of the technical restrictions of previous systems can nowadays be alleviated by new generations of high quality and high framerate cameras, TOF (time of flight) depth sensors, and advanced projectors and displays.